The objective of this study is to study the survival characteristics of human sickle cell erythrocytes in a heterologous species and to evaluate various modalities of therapy. Some of the specific areas to be studied would include (a) the relationship of hypoxia to intravascular trapping of sickle cells, (b) the macrocirculatory changes in the initiation of the sickling, (c) effect of hyperbaric oxygen on sickle cell survival, (d) the effectiveness of carbamylation and other forms of therapy on sickle cell erythrocyte survival, and (e) the survival characteristics of other types of intrinsically defective human erythrocytes. The proposed method involves the use of rats, guinea pigs and rabbits following (a) ethyl palmitate blockade of the RES, and (b) inactivation of the C3 component of complement through the use of a cobra venom factor. Test erythrocytes are labeled with 51Cr and following their injection into prepared rats tail blood samples are removed at appropriate intervals during the next 24-48 hours for radioassay. These data provide the basis for construction of survival curves. The survival characteristics of the blood are altered through (a) pretreatment of the red cells prior to transfusion or (b) manipulation of the recipient animal following transfusion. The rat model system employed permits studies on sickle cells that would not be feasible in man. BIBLIOGRAPHIC REFERENCES: Castro, O., Osbaldiston, G. W., Orlin, J., Roth, R., and Finch, S. D.: Sickle cell erythrocyte survival after heterologous transfusion. J. Lab. Clin. Med. 1976, in press.